1. Field of the Invention
The invention relates to a matrix pin print head of the biased construction with a base plate made of a soft-magnetic material, an annular permanent magnet disposed on the base plate, a distance spacer ring made of a soft-magnetic material, a spring which, in each case, is tensioned and clamped radially outwardly, where, in each case, an armature body is attached radially inwardly at said spring, which armature body, in each case, can be biased against the core of an electromagnetic coil, disposed in each case on the base plate.
2. Brief Description of the Background of the Invention Including Prior Art
Such a matrix pin print head is in general equipped with a permanent magnet in contrast to the matrix pin print head of the hinged clapper armature type. A first main magnet flux circuit is effected and composed via the core of an electromagnetic coil, via the armature body or, respectively, the armature, the distance spacer ring, the permanent magnet, the base plate and returned back.
It has been proposed in the German Patent Application Laid Open DE 3,110,798 to create a parallel resistor, which is formed by a short-circuit body, as a side magnet flux circuit for optimizing the main magnet flux circuit. The side magnet flux circuit reduces the main magnet flux circuit to an intensity such that a low current passage (ampere winding number) of the electromagnetic coil is sufficient to completely balance the magnetic field of the permanent magnet, i.e. to shoot off the armature body attached to the spring, at which armature body the print element is attached, such that the print element generates a dot on the paper.
The so-called optimization of the field line guide allows to reduce the product, resulting from current intensity times number of turns, such that a construction can be produced either with a lower current intensity or with a smaller number of turns of the copper wire, or with a somewhat less reduced current intensity and a somewhat less reduced number of turns. In this case, a reduced current intensity is associated with a situation of a reduced waste heat dissipation.
This optimization of the holding power of the permanent magnet can now be set, according to the conventional teaching, by a magnetic property of the side flux circuit (shunt ring) such that the magnetic resistance of the set-up yoke increases with increasing temperature of the set-up yoke forming the side magnet ring.
Another conventional teaching of the German Patent DE-PS 3,644,185, which is also concerned with the optimization of the holding power, resolves the optimization problem in that the thickness of the side magnet ring (shunt ring) is variable depending on the main-series magnet circuit with the permanent magnet and, for tuning to the working or operating point, a side magnet shunt ring with a corresponding thickness is employed.
Based on experience of long standing and based on experiments, it has however been determined that the capabilities of a biased system permanent magnet/electromagnet does not only depend on the optimization of the holding power of the permanent magnet, but also on the simultaneous current passage through two neighboring or several electromagnetic coils. In particular, a possible simultaneous printing of two print dots in a character, such as, for example, in a letter "E", "F" and others, results in a mutual flux penetration of several electromagnetic fields, where neighboring magnetic fields act in opposed directions and result in a substantially deteriorated lifting or, respectively, displacement of the magnetic field. It has been found, that the print speed is decreased by an amount of about 30% based on this mutual influencing of the magnetic field.